The present invention relates to a device for adjusting flow rate of combustion air flowing into a gas turbine combustor and, more particularly, to a mechanism enabling an improvement of durability of movable parts in a combustion air flow rate adjusting device in which a cylindrical regulating ring fitted about an outer peripheral surface of an inner cylinder of a gas turbine combustor is translated axially of the inner cylinder to vary an opening area of air intake ports formed in the peripheral wall of the inner cylinder, thereby adjusting the flow rate of air passing through the air intake ports.
A premixed staged combustion system is known, as disclosed in, for example, U.S. Serial No. 917,973 filed on October 14, 1986, now Pat. No. 4,766,721, in which first stage fuel nozzles are provided for forming pilot flames at a head of a gas turbine combustor, and second stage fuel nozzles are provided at a location downstream of combustion gas for supplying premixture. Fuel is supplied to only the first stage fuel nozzles, or to both first and second stage fuel nozzles, depending upon load on the gas turbine, so that low temperature combustion is effected in the entire load range of the gas turbine.
The above-described premixed staged combustion system is advantageous in that production of nitrogen oxides (NOx) in the combustion gas is reduced because of the low temperature combustion. However, the premixed staged combustion system has such a problem that, in the course of shifting of the gas turbine load from a low load range to a high load range, when the fuel is initiated to be supplied from the second stage fuel nozzles, the second stage fuel is difficult to be completely burnt so that unburnt components such as CO, HC and the like are emitted.
Further, a gas turbine for driving a generator has the following problem. That is, the gas turbine is operated at a constant speed, regardless of load, as the generator reaches a synchronous speed. However, since the amount of fuel supplied increases substantially in proportion to the load, the mixture ratio between fuel and air varies depending upon the load. The reason for this is that air supplied to the combustor of the gas turbine is forcibly delivered by a compressor directly connected to the gas turbine rotor and, therefore, a substantially constant amount of air is given to the combustor when the rotational speed of the rotor is constant.
For the combustor in which two stage combustion is effected, it is necessary to control and regulate the fuel and air such that the ratio between them in particular at the second stage is maintained at a substantially constant proportion regardless of the load, to perform always steady combustion.
In the above-mentioned prior application Serial No. 917, 973, the control of fuel and air is effected by extraction of air to be supplied to the second stage fuel and by provision of a ring at air intake ports for regulating an opening area thereof. The extraction method is disadvantageous in that the total efficiency of the gas turbine is lowered because the extracted air is thrown away to the outside without passing through the gas turbine. The method of provision of the regulating ring at the air intake ports has no such loss that the compressed air is uselessly thrown away to the outside, but requires a mechanism for moving the ring provided adjacent an inner cylinder of the combustor. The moving mechanism for the ring is not described in detail in the above-mentioned prior application, but as a moving mechanism of such kind, a transmission mechanism is generally employed which comprises levers and links.
The transmission mechanism comprising links and levers has sliding parts around connecting pins, and wear occurs on the sliding parts. Since, in particular, the sliding parts within the gas turbine combustor are exposed to high temperature, it is difficult to supply lubricating oil to the sliding parts so that wear cannot be prevented from occurring on the sliding parts. Once the wear occurs, plays are enlarged between various components, resulting in a reduction in adjusting accuracy. This deteriorates the combustion performance.